13
Usage Guide:
This command can be used for explaining and describing a prefix-list, e.g. the
application and attention matters of the prefix-list
Example:
Switch#config terminal
Switch(config)#ip prefix-list 3 description This list is used by BGP
1.2.3.2 ip prefix-list seq
Command: ip prefix-list <list_name> [seq <sequence_number>] <deny | permit> < any |
ip_addr/mask_length [ge <min_prefix_len>] [le <max_prefix_len>]>
no ip prefix-list <list_name> [seq <sequence_number>] [<deny | permit> < any
| ip_addr/mask_length [ge <min_prefix_len>] [le <max_prefix_len>]>]
Function:
Configure the prefix-list. The “
no ip prefix-list <list_name> [seq
<sequence_number>] [<deny | permit> < any | ip_addr/mask_length [ge <min_prefix_len>]
[le <max_prefix_len>]>]
” command deletes the prefix-list.
Parameter: <list _name>
is the name of prefix-list, “seq” shows the following parameters is the
sequence number,
<sequence_number>
is the sequence number, “deny” means deny this
route, “permit” means permit this route, “any” means adaptive to all packets with any prefix as
well as any mask length,
ip_addr/mask_length
shows the prefix address (dotted decimal
notation) and the length of mask, “ge” means greater than or equal to,
<min_prefix_len>
is the
minimum length of prefix to be matched
（
ranging between 0
～
32
）
, “le” means less than or equal
to,
<max_prefix_len>
is the maximum length of prefix to be matched
（
ranging between 0
～
32
）
.
Default:
None.
Command Mode:
Global Mode
Usage Guide:
A prefix-list is identified by a prefix-list name. Each prefix-list may include several
items each of which independently specifies a matching scope of network prefix-list type which is
identified with a
sequence-number. sequence-number
specifies the sequence of matching check
in the prefix-list. In the matching process the switch check in turn every items identified by
“
sequence-number
” ascending. Once certain item obtains the conditions then the prefix-list filter
is passed (without proceeding into the next item check)
Attentions should be paid on that at least one item match mode should be “permit” when
more than one prefix-list items is defined. The deny mode items can be previously defined so to
remove the unsuitable routing messages fast. However if all items are at deny mode then none
of the routes would be able to pass the filter of this prefix-list. We here can define a “permit
0.0.0.0/0 ge
0 le
32” item after several defined “deny mode” items so to grant the passage for all
other routing messages.
Example:
Switch#config terminal
Switch(config)#ip prefix-list mylist seq 12345 deny 10.0.0.0/8 le 22 ge 14